So with my increase in trail running I'm finding out systems that work and don't and I'm curious to hear feedback from others.

On my last run (4 miles) I got to a clear cut area with it was raining really hard. While I'm running the rain keeps me cool and I actually like it but when I stop (for periods greater than 5 mins) my body cools down and then I can get chilled. So I took with me a AMK heatsheets blanket and just wrapped it around me and covered the top of my head while I stood there. I was surprised that I found this quite comfortable and it helped me stay a little warmer then usual.

Has anyone else tried using a "wrap" approach in terms of rainwear for short periods of time? Success or failure?

For shorter local runs like the 4 mile one you describe, I typically don't bring any sort of rain protection. I just get wet and muddy and try not to stop and get cold. I don't like to carry anything with me on those shorter runs. I have some bike style shirts with rear pockets that I will occasionally put a wind shirt in if I plan on stopping, say above treeline for a rest or something. On longer intervals I wear a running pack to carry clothing, food, and water.

For longer (like day-long) adventures I usually will plan in advance and try to take advantage of nicer weather when I can. But that doesn't always work out. If it is almost guaranteed to rain I bring a hooded rain jacket with me. If the liklihood of rain is rather low, I might chance it with just a wind jacket, but I recently snagged a 6oz WPB hooded jacket that packs down to almost wind shirt size, so that would probably be my go-to choice for a potentially rainy day (forecast calls for 30-60% chance). For a higher probability of rain I will bring a heavier but more breathable jacket that works better on the move.

There are a lot of variables that will affect my decision, however. Temperature is a huge one. The above scenarios I'm probably looking at 50+ degrees. Below that, I'll be a lot more cautious on a long day far from shelter. Also if its very warm out and looks like just a passing storm, I'm usually fine with getting rained on, counting on being able to dry out after the storm passes. Usually these passing storms are a pleasant relief and very refreshing.

Take note that when I talk about wearing a jacket for a long day running adventure, I am typically moving much slower than my short run pace, so it's tolerable to wear a jacket on the move. I need to get better at proactively putting the jacket on though, to keep from getting rained on in the first place. It's nicer to NOT be wet all day if it's avoidable. I also don't usually stop for longer than a couple of minutes at a time, even for a 15 hour day. That can make a big difference for maintaining warmth while wet.

I tried and found I really don't like ponchos.

I almost never bring or wear rain pants unless I'm out for more than a day. I typically wear shorts with a boxer-brief liner built in. I'm usually comfortable enough even if they're soaking wet.

I have some experience using a "wrap" approach. Last spring I headed out to hike a section of the PCT from Big Bear to Swarthout Canyon Road. I got some snow and rain on several of those days. I forgot my umbrella and had only rain pants. I wrapped my polycryo ground sheet around me to protect my torso. It was suitably effective. The rain wasn't torrential. It was mostly wind-driven constant spatter. I felt the polycryo kept me warm and dry enough.

I had an opportunity to use this system again recently. I used a vinyl emergency poncho in the rain. It lasted less than 5 minutes. The brush on the trail tore it to shreds. I ended up getting completely drenched and it was a cold, solid rain. I wore the polycryo wrap the following morning mostly as additional warmth over my wet clothing. It helped.

I'm thinking that since the polycryo is so much more durable than crappy vinyl emergency ponchos and because it's so cheap and light and folds small, perhaps I'll attempt to make an actual poncho from it.

After postin his thread I did a lot of experimenting and this is what I found works best for me.

I took a Glad garbage from under the sink and cut two arm holes and a head hole and then cut off the bottom 3" where the orange tie goes. It wears like a vest and obviously doesn't have a hood but I wear my merino hat and I'm fine. This is by far the lightest option and it packs so freaking small I hardly notice it in my pocket while I run. Even though my arms get wet my shirt underneath is completely dry. My wife laughs everytime I talk about how much Iike my garbage bag but that's ok to me :)

And the clarify I only use this when it's raining AND cold. If raining and warm then I won't bother with anything.